SAO might be reality soon anyway with advances in technology yet to come. If i were to choose it would be.. Probably naruto because im drawing a blank. Mastering my own jutsu would be fun, through hard work i could go far but it would be a tough world. :]

X/1999? I've always wanted to be bishonen as hell and have awkwardly proportioned limbs... oh and fight other bishonen people to the death to decided the fate of the world.... annnnd hold on to severed heads while yelling out their names;
"FUUUUUUUUUMMMMMMAAAAAAAAAAAAAAAAAA..."

SAO so long as the whole being stuck in the game, hoping I don't die in real life, sort of thing doesn't happen. I live on my own and only get visitors once a week maybe every other week due to conflicting work schedules, so no one would find me deteriorating in real life. XD

Aside from that though... I would probably say Pokemon, even though I stopped paying attention to it after the like Red and Yellow gameboy versions.